Non-Patent Literature 1 discloses a scheme of generating illumination light having a uniform light intensity distribution within a certain surface perpendicular to the optical axis. The scheme of generating such illumination light includes an example of a scheme of modulating input light having a light intensity distribution according to a Gaussian distribution by a spatial light modulator. In this scheme, a computer generated hologram (CGH), which makes the light intensity distribution uniform in a predetermined range within a light converging surface, is presented by the spatial light modulator. A CGH to be presented on the spatial light modulator is designed on the basis of a function of one-dimensional ξ shown in the following Equations (1) (ϕ(ξ) is a phase value presented at a position ξ).
                              [                      Math            .                                                  ⁢            1                    ]                ⁢                                                                                                                          d              ⁢                                                          ⁢                              φ                ⁡                                  (                  ξ                  )                                                                    d              ⁢                                                          ⁢              ξ                                =                      B            ⁢                                          ∫                0                ξ                            ⁢                                                I                  ⁡                                      (                                          ξ                      ′                                        )                                                  ⁢                d                ⁢                                                                  ⁢                                  ξ                  ′                                                                    ⁢                                  ⁢                              I            ⁡                          (                              ξ                ′                            )                                =                      e                          -                              ξ                ′2                                                                        (        1        )            